Transducers of many kinds are commonly used in connection with musical instruments in order to allow them to be amplified, recorded or to remotely control a second instrument.
Many musical instruments have one or more vibrating elements such as a reed, a membrane or a string. Reeds and membranes generally vibrate in a fixed plane of vibration but vibrating strings and other rod-like vibrating elements usually vibrate in different planes. The string of a bowed instrument characteristically vibrates in a plane parallel to the surface of the bow. The string of a plucked instrument will start vibrating in a plane parallel to the direction of plucking but will change its plane of vibration. Characteristically, the plane of vibration of the string of a plucked or hammered instrument will constantly change and if it is permitted to vibrate long enough without being damped or replayed, the string will vibrate in constantly changing planes through 360 degrees.
Pickups of the prior art typically produce a signal, the strength of which is proportional to the vector of the plane of vibration of the vibrating element in the direction of maximum sensitivity of the pickup. To attain natural reproduction of the sound produced by a vibrating element of a musical instrument, the amplitude of the pickup signal should be the same for a given amplitude of vibration, irrespectively of the plane of vibration of the vibrating element. Virtually all contact and proximity transducers of the prior art have heretofore exhibited a significantly different response to the vibrations of a vibrating element in various planes of vibration.
U.S. Pat. No. 3,301,936 issued to Carman et al describes a mechanico-electrical pickup for an instrument string having maximum sensitivity in the direction of the axis of the string. Such a pickup responds to changes in the tension of the string and although it responds equally in all planes of vibration, the signal produced in response to a simple vibration of the string will be an octave above the frequency of this simple vibration. This occurs because changes in the tension of the string occur at twice the rate of the string vibration.
Such frequency doubling tends to give the pickup a thin sound and is not desirable from a musical standpoint. It is generally agreed to in the prior art that a pickup should accurately transduce the fundamental frequency of the monitored vibrations in order to produce a natural sounding tone signal.
A first problem exists when using pickups of the prior art in a stringed instrument such as a bass guitar, that "dead notes" are sometimes encountered because the pickups fail to respond in the plane in which the fundamental frequency of the remanent string vibrations has settled shortly after the attack of a played note. A second problem exists with virtually any pickup of the prior art, that the direction of excitation of the string influences the sound of the attack of the note to a high degree. A third problem exists when detecting the fundamental frequency of the played note using pickups of the prior art for the purpose of controlling a second instrument such as a music synthesizer, that these pickups tend to produce either a very reduced amplitude or a frequency doubling effect in response to string vibrations in certain planes, which makes the detection significantly more difficult if not impossible to perform in these instances.
It is therefore a broad object of the present invention to provide a pickup for a stringed instrument which responds approximately equally in all planes of vibration of a vibrating element.
It is a more specific object of the present invention to provide a pickup which accurately transduces the frequencies of vibration of the vibrating element, irrespectively of the plane of such vibrations.
It is a further object of the present invention to provide a pickup for an instrument string which is approximately equally responsive in all directions of excitation of the vibrating element.
It is a still further object of the present invention to provide a pickup which produces a strong fundamental frequency corresponding to that of the vibrations of the vibrating element.